Right now I have on an open air filter, and have seen heat shielded filters as well. What differences are there in terms of performance, or are they basically the same? Which would be more preferable?

well the idea is to cool the air intake as much as possible so a heat sheilded filter would work slightly better than an open intake, but for the best gains, go with a cold air intake from AEM or Iceman.

True that CRXLVR!!! True that! ;)

Thanks for the info. Actually, I got a bit confused: my friend said the open one is better, as it can get air in more. I think the heat shielded one is more practical, though, aside from the reason provided here: when you clean your engine, you don't have to worry about the filter getting wet, unlike that of the open air filter.

If u are worried about getting a filter wet when cleaning an engine, simply take it out and cover the opening while cleaning. Dont let that be your reason for not sticking with an open air filter element. Basically, the idea of the open air is to increase air volume through the intake. The idea of the heat shield is to block most of the hot air from the engine because hot air is less dense and thus has less oxygen particles in the same volume of air than colder air would.

In my opinion, the heat shield idea is stupid. If you still have the filter in the engine bay, it is going to suck up hot air regardless of what you cover the filter with. The heat shield may stop some hot air from entering the intake, but there is no cooler air coming in anywhere else so it just decreases air flow in general and i wouldnt be surprised to see a decrease in hp from stock after installing it.

I think that a high performance drop in filter (like K&N) for the stock air box would have about the same gains and would be much cheaper. The only way for the heat shield to be effective is for there to be an inlet for air from outside the car to get to the intake. That is what makes the CAI systems the most effective.